Amgen Inc. edged out Wall Street expectations with a 15% rise in first-quarter net income, but lowered its profit estimate for the full year because of a delay in approval for its highly anticipated anemia treatment, Aranesp.

Amgen, of Thousand Oaks, Calif., had originally expected the U.S. Food and Drug Administration to approve Aranesp within 15 months of its regulatory filing in December 1999. Instead, the FDA appears to be taking...